Case IH 19546 – Engine Control Module (ECM) or Dosing Control Unit (DCU): Monitoring of NOx signal readiness

This fault code indicates that the engine's control system is monitoring the Nitrogen Oxide (NOx) sensor, but the sensor is failing to reach its 'ready' state within the expected timeframe or its signal readiness check has failed. This is a critical emissions fault related to the Selective Catalytic Reduction (SCR) system.

• Tier 4b
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Puma 150
• Puma 165
• Puma 185
• Puma 200
• Puma 220
• Maxxum series
• Steiger
• Steiger Quadtrac
• Combine 5140
• Combine 6140
• Combine 7140
• Combine 7240
• Combine 8240
• Combine 9240
• Patriot 2250
• Patriot 3240
• Patriot 3340
• Patriot 4440
• Titan 3040
• Titan 3540
• Titan 4040
• Titan 4540
• N-Series Loader Backhoes
• 721F Wheel Loaders

1. 1

   Check for Accompanying Codes: Look for related NOx sensor circuit codes (e.g., 19547 SRC Max error, 19548 SRC Min error, 19549 Open circuit, 19551 Short circuit) which point directly to wiring failures rather than a failed sensor.

2. 2

   Wiring and Connector Inspection: Inspect the wiring harness leading to the NOx sensor (both upstream and downstream of the SCR catalyst). Look for melted wires, corrosion in the 5-pin connector, or loose pins.

3. 3

   Power and Ground: Verify that the NOx sensor is receiving proper voltage (typically 12V or 24V depending on the machine system) and has a solid ground.

4. 4

   Exhaust Leaks: Inspect the exhaust pipe upstream of the NOx sensor. Exhaust leaks can introduce excess oxygen or allow heat to escape, preventing the sensor from reaching its required operating temperature to signal 'readiness.'

5. 5

   DEF Quality: Ensure the DEF/AdBlue fluid is uncontaminated and at the correct concentration, as poor fluid can cause erratic SCR performance and trigger NOx plausibility/readiness faults.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes. Allow the exhaust system to cool completely.

2. 2

   Locate the Sensor

   Locate the faulty NOx sensor on the exhaust aftertreatment pipe (the diagnostic tool will specify if it is the upstream or downstream sensor).

3. 3

   Disconnect

   Unplug the electrical connector from the machine's wiring harness. Free the wire from any retaining clips.

4. 4

   Removal

   Using a specialized NOx sensor socket or a 22mm wrench, carefully unscrew the sensor from the exhaust bung. Note: If the sensor is seized, apply penetrating oil and allow it to sit before applying force to avoid stripping the exhaust bung threads.

5. 5

   Installation

   Thread the new NOx sensor into the exhaust bung by hand to prevent cross-threading. (Most new OEM sensors come with anti-seize pre-applied to the threads; if not, apply a small amount, ensuring none gets on the sensor probe).

6. 6

   Torque

   Tighten the sensor to the manufacturer's specified torque (usually around 50 Nm / 37 lb-ft).

7. 7

   Reconnect

   Route the wiring harness exactly as it was from the factory, keeping it away from extreme heat sources. Plug in the electrical connector.

8. 8

   Clear Codes and Test

   Reconnect the battery. Use the Case IH Electronic Service Tool (EST) to clear the fault codes. You must perform a forced stationary regeneration or operate the machine under load to allow the exhaust to reach operating temperature so the new sensor can initialize and verify readiness.